Changes in African American and Latinx Students’ Perceived Ethnic–Racial Discrimination During the Middle School Transition Year

The middle school transition year poses known challenges to early adolescent adjustment, particularly for students from ethnic and racial minoritized backgrounds who face ethnic and racial discrimination from school personnel and classmates. Drawing on a sample of 711 African American and Latinx sixth-grade students attending 17 schools, we employed latent class analysis and latent transition analysis to explore the nature of and changes to perceived ethnic and racial discrimination during the beginning and end of sixth grade. We also examined the possibility that perceived ethnic–racial discrimination could be diminished through a school-based, universal program for teachers to improve the school ecology. Findings revealed four distinct classes concerning perceived ethnic–racial discrimination, with patterns over time highlighting the malleability of perceived ethnic–racial discrimination during the first year of middle school. Findings provide direct implications for understanding and improving ethnic and racial minoritized students’ school experiences at the middle school transition

Sputter Deposition of Semiconductor Superlattices for Thermoelectric Applications

Theoretical dramatic improvement of the thermoelectric properties of materials by using quantum confinement in novel semiconductor nanostructures has lead to considerable interest in the thermoelectric community. Therefore, we are exploring the critical materials issues for fabrication of quantum confined structures by magnetron sputtering in the lead telluride and bismuth telluride families of materials. We have synthesized modulated structures from thermoelectric materials with bilayer periods of as little as 3.2 nm and shown that they are stable at deposition temperatures high enough to grow quality films. Issues critical to high quality film growth have been investigated such as nucleation and growth conditions and their effect on crystal orientation and growth morphology. These investigations show that nucleating the film at a temperature below the growth temperature of optimum electronic properties produces high quality films. Our work with sputter deposition, which is inherently a high rate deposition process, builds the technological base necessary to develop economical production of these advanced materials. High deposition rate is critical since, even if efficiencies comparable with CFC based refrigeration systems can be achieved, large quantities of quantum confined materials will be necessary for cost-competitive uses

Economic Fluctuations and Diffusion

Stock price changes occur through transactions, just as diffusion in physical systems occurs through molecular collisions. We systematically explore this analogy and quantify the relation between trading activity - measured by the number of transactions $N_{\Delta t}$ - and the price change $G_{\Delta t}$, for a given stock, over a time interval $[t, t+\Delta t]$. To this end, we analyze a database documenting every transaction for 1000 US stocks over the two-year period 1994-1995. We find that price movements are equivalent to a complex variant of diffusion, where the diffusion coefficient fluctuates drastically in time. We relate the analog of the diffusion coefficient to two microscopic quantities: (i) the number of transactions $N_{\Delta t}$ in $\Delta t$, which is the analog of the number of collisions and (ii) the local variance $w^2_{\Delta t}$ of the price changes for all transactions in $\Delta t$, which is the analog of the local mean square displacement between collisions. We study the distributions of both $N_{\Delta t}$ and $w_{\Delta t}$, and find that they display power-law tails. Further, we find that $N_{\Delta t}$ displays long-range power-law correlations in time, whereas $w_{\Delta t}$ does not. Our results are consistent with the interpretation that the pronounced tails of the distribution of $G_{\Delta t} are due to$w_{\Delta t}$, and that the long-range correlations previously found for$| G_{\Delta t} |$are due to$N_{\Delta t}$.Comment: RevTex 2 column format. 6 pages, 36 references, 15 eps figure

Distance education use in rural schools

A national survey of rural school systems in the United States was conducted to determine the extent to which distance education is being utilized by rural schools, the technologies used, the curriculum areas impacted, the perceived needs for distance education, their satisfaction with distance education, and the barriers to distance education use. Data were collected through telephone surveys with 394 school districts selected at random. Most rural school districts were currently using distance education. The subjects most often offered by distance education were math, foreign language, and English. A large majority of the districts indicated satisfaction with distance education courses; almost half stated they were very satisfied. The majority of students who enrolled in distance education courses completed these courses. Two-thirds of the districts indicated a need for additional distance education courses. Only a small portion of school districts indicated they are able to offer all the advanced and enrichment classes that students need without using distance education. The large majority of the districts did not see connectivity as a barrier to distance education use. Common barriers were funding, scheduling, and difficulty implementing distance education courses. The two most common formats for distance education courses in rural schools were two-way videoconferencing courses and online courses. Implications for future research are discusse

Sputter deposition of semiconductor superlattices for thermoelectric applications

Theoretical dramatic improvement of the thermoelectric properties of materials by using quantum confinement in novel semiconductor nanostructures has lead to considerable interest in the thermoelectric community. Therefore, we are exploring the critical materials issues for fabrication of quantum confined structures by magnetron sputtering in the lead telluride and bismuth telluride families of materials. We have synthesized modulated structures from thermoelectric materials with bilayer periods of as little as 3.2 nm and shown that they are stable at deposition temperatures high enough to grow quality films. Issues critical to high quality film growth have been investigated such as nucleation and growth conditions and their effect on crystal orientation and growth morphology. These investigations show that nucleating the film at a temperature below the growth temperature of optimum electronic properties produces high quality films. Our work with sputter deposition, which is inherently a high rate deposition process, builds the technological base necessary to develop economical production of these advanced materials. High deposition rate is critical since, even if efficiencies comparable with CFC based refrigeration systems can be achieved, large quantities of quantum confined materials will be necessary for cost-competitive uses

Endothelial dysfunction in renal transplant recipients maintained on cyclosporine

Background: Hypertension is almost universal following renal transplantation and may contribute to the already poor cardiovascular prognosis of this group. Cyclosporine-induced hypertension is a particular problem and has variously been attributed to increased sympathetic nerve activity, salt and water retention, and increased circulating endothelin levels. However, the effects of cyclosporine on the l-arginine/nitric oxide (NO) system in vivo in humans are unknown. In this present study, we examined basal and stimulated NO production from the vascular endothelium in cyclosporine-treated renal transplant recipients using the technique of forearm venous plethysmography.<p></p> Methods: In study 1, stimulated NO production was assessed in 9 cyclosporine-treated renal transplant recipients (CsA), 7 azathioprine-treated renal transplant recipients (AZA), and 12 controls, using carbachol (an endothelium-dependent vasodilator) and sodium nitroprusside (an endothelium-independent vasodilator). In study 2, basal NO production was assessed in 9 cyclosporine-treated patients and 11 controls using l-NMMA (inhibits NO synthase), with norepinephrine as a control vasoconstrictor. Drugs were infused into the nondominant forearm through a sterile 27-gauge needle, and changes in forearm blood flow (FBF) were measured using venous occlusion plethysmography.<p></p> Results: In study 1, sodium nitroprusside caused a similar dose-dependent increase in FBF in all groups. However, the median (range) percentage increase FBF to carbachol (3 μg/min) was markedly reduced in the CsA patients (188.8; 72.5 to 385.1) compared with AZA patients (378.1; 124.0 to 548.9; P = 0.042) and to controls (303.8; 124.8 to 813.3; P = 0.028). In study 2, the maximum percentage reduction in FBF to l-NMMA (4 μmol/min) was less pronounced in CsA patients (−19.5; −4.7 to −63.1) compared with controls (− 39.5; −15.7 to −52.8; P = 0.056), and while controls vasoconstricted to the maximum dose of norepinephrine (240 pmol/min) as expected (−26.9; −1.4 to −38.6), CsA patients as a group tended to vasodilate (7.9; −36.8 to 92.6; P = 0.02).<p></p> Conclusion: These data demonstrate impaired stimulated and basal NO production in CsA patients, indicating endothelial dysfunction. This may predispose patients to atherosclerosis and may be involved in the etiology of post-transplant hypertension